Method and apparatus for performing directional re-scan of an adaptive antenna

ABSTRACT

An antenna for use with a receiver in a wireless communications system includes antenna elements for generating antenna patterns, and a first module for applying weights to a signal received at each of the antenna elements to generate a selected one of the antenna patterns. A second module detects the received signal at each of the antenna elements. A combiner combines the received signal detected at each of the antenna elements to produce a combined received signal for a selected antenna pattern. A third module determines a signal quality metric for the combined received signal at each selected antenna pattern. The first module is responsive to the determined signal quality metrics for adjusting the weights to generate a preferred antenna pattern.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.09/776,396 filed Feb. 2, 2001 now U.S. Pat. No. 6,792,290, which is aContinuation-In-Part of U.S. patent application Ser. No. 09/579,084filed May 25, 2000 now U.S. Pat. No. 6,304,215, which is a divisionalapplication of U.S. patent application Ser. No. 09/210,117 filed Dec.11, 1998 now U.S. Pat. No. 6,100,843, which is a continuationapplication of U.S. patent application Ser. No. 09/157,736 filed Sep.21, 1998 now abandoned the entire teachings of which are incorporatedherein by reference.

FIELD OF THE INVENTION

This invention relates to mobile (or portable) cellular communicationsystems, and more particularly to an antenna apparatus for use by mobilesubscriber units to provide beam forming transmission and receptioncapabilities.

BACKGROUND OF THE INVENTION

Code division multiple access (CDMA) communication systems providewireless communications between a base station and one or more mobilesubscriber units. The base station is typically a computer-controlledset of transceivers that are connected to a land-based public switchedtelephone network (PSTN). The base station includes an antenna apparatusfor sending forward link radio frequency signals to the mobilesubscriber units. The base station antenna also receives reverse linkradio frequency signals transmitted from each mobile unit. Each mobilesubscriber unit also contains an antenna apparatus for the reception ofthe forward link signals and for transmission of the reverse linkssignals. A typical mobile subscriber unit is a digital cellulartelephone handset or a personal computer coupled to a cellular modem. InCDMA cellular systems, multiple mobile subscriber units may transmit andreceive signals on the same frequency, but with different modulationcodes, to distinguish signals sent to or received from individualsubscriber units.

The most common type of antenna for transmitting and receiving signalsat a mobile subscriber unit is a monopole or omnidirectional antenna.This type of antenna consists of a single wire or antenna element thatis coupled to a transceiver within the subscriber unit. The transceiverreceives reverse link signals to be transmitted from circuitry withinthe subscriber unit and modulates the signals onto a carrier signal at aspecific frequency assigned to that subscriber unit. The modulatedcarrier signal is then transmitted by the antenna element. Forward linksignals received by the antenna element at a specific frequency aredemodulated by the transceiver and supplied to processing circuitrywithin the subscriber unit.

The signal transmitted from a monopole antenna is omnidirectional innature. That is, the signal is sent with substantially the same signalstrength in all directions in a generally horizontal plane. Reception ofa signal with a monopole antenna element is likewise omnidirectional. Amonopole antenna does not differentiate in its ability to detect asignal in one azimuth direction versus detection of the same or adifferent signal coming from another azimuth direction. Generally, amonopole antenna does not produce significant radiation in the elevationdirection. The antenna pattern is commonly referred to as a donut shapewith the antenna element located at the center of the donut hole.

A second type of antenna that may be used by mobile subscriber units isdescribed in U.S. Pat. No. 5,617,102. The system described thereinprovides a directional antenna comprising two antenna elements mountedon the outer case of a laptop computer, for example. The system includesa phase shifter attached to each element. The phase shifter may beswitched on or off to effect the phase of signals transmitted orreceived during communications to and from the computer. By switchingthe phase shifters on and regulating the amount of phase shift impartedto the signals input thereto, the antenna pattern (which applies to boththe receive and transmit modes) may be modified to provide aconcentrated signal or beam in the selected direction. This is referredto as an increase in antenna gain or directionality. The dual elementantenna of the cited patent thereby directs the transmitted signal intopredetermined quadrants or directions to allow for changes inorientation of the subscriber unit relative to the base station, whileminimizing signal loss due to the orientation change. In accordance withthe antenna reciprocity theorem, the antenna receive characteristics aresimilarly effected by the use of the phase shifters.

CDMA cellular systems are also recognized as being interference limitedsystems. That is, as more mobile subscriber units become active in acell and in adjacent cells, frequency interference becomes greater anderror rates increase. As error rates increase, to maintain signal andsystem integrity, the operator must decrease the maximum data ratesallowable to all users. In lieu of decreasing all user's data rates, theCDMA system operator can decrease the number of active mobile subscriberunits, thus clearing the airwaves of potential interferers. Forinstance, to increase the maximum available data rate by a factor oftwo, the number of active mobile subscriber units is decreased by onehalf. However, this is rarely an effective mechanism to increase datarates because system users generally do not have priority assignments tobe utilized in determining which users should be dropped from thesystem.

SUMMARY OF THE INVENTION

Problems of the Prior Art

Various problems are inherent in prior art antennas used on mobilesubscriber units in wireless communications systems. One such problem iscalled multipath fading. In multipath fading, a radio frequency signaltransmitted from a sender (either a base station or mobile subscriberunit) may encounter interference on route to the intended receiver. Thesignal may, for example, be reflected from objects, such as buildings,that are not in the direct transmission path, but that redirect areflected version of the original signal to the receiver. In suchinstances, the receiver receives two versions of the same radiofrequency signal; the original version and a reflected version. Eachreceived signal is at the same frequency, but the reflected signal maybe out of phase with the original due to the reflection and consequentlonger transmission path. As a result, the original and reflectedsignals may partially cancel each other (destructive interference),resulting in fading or dropouts in the received signal; hence the termmultipath fading.

Single element antennas are highly susceptible to multipath fading. Asingle element antenna has no way of determining the direction fromwhich a transmitted signal is sent and cannot be tuned or attenuated tomore accurately detect and receive a signal arriving from any particulardirection. Its directional pattern is fixed by the physical structure ofthe antenna components.

The dual element antenna described in the aforementioned reference isalso susceptible to multipath fading due to the symmetrical and opposingnature of the hemispherical lobes formed by the antenna pattern when thephase shifter is activated. Since the lobes created in the antennapattern are more or less symmetrical and in opposing directions, asignal reflected so that it arrives at the reverse antenna lobe can bereceived with nearly as much power as the original signal that isreceived directly at the forward antenna lobe. That is, if the originalsignal reflects from an object beyond or behind the intended receiver(with respect to the sender) and reflects back to the intended receiverfrom the opposite direction as the directly received signal, a phasedifference in the two signals can create destructive interference due tomultipath fading.

Another problem present in cellular communication systems is inter-cellinterference. Most cellular systems are divided into individual cells,with each cell having a centrally-located base station. The placement ofeach base station is arranged such that neighboring base stations arelocated at approximately sixty degree intervals from each other. Inessence, each cell may be viewed as a six sided polygon with a basestation at the center. The edges of each cell adjoin each other and agroup of cells form a honeycomb-like image if each cell edge were to bedrawn as a line and all cells were viewed from above. The distance fromthe edge of a cell to its base station is typically driven by themaximum amount of power that is to be required to transmit an acceptablesignal from a mobile subscriber unit located near the edge of the cellto that cell's base station (i.e., the power required to transmit anacceptable signal a distance equal to the radius of one cell).

Intercell interference occurs when a mobile subscriber unit near theedge of one cell transmits a signal that crosses over that edge into aneighboring cell and interferes with communications taking place withinthe neighboring cell. Typically, intercell interference occurs when thesame or similar frequencies are used for communications in neighboringcells. The problem of intercell interference is compounded by the factthat subscriber units near the edges of a cell typically use highertransmit powers so that the signals they transmit can be effectivelyreceived by the intended base station located at the cell center.Consider that the signal from another mobile subscriber unit locatedbeyond or behind the intended receiver may arrive at the base station atthe same power level, representing additional interference.

The intercell interference problem is exacerbated in CDMA systems, sincethe subscriber units in adjacent cells may typically be transmitting onthe same frequency. For example, generally, two subscriber units inadjacent cells operating at the same carrier frequency but transmittingto different base stations will interfere with each other if bothsignals are received at one of the base stations. One signal appears asnoise relative to the other. The degree of interference and thereceiver's ability to detect and demodulate the intended signal is alsoinfluenced by the power level at which the subscriber units areoperating. If one of the subscriber units is situated at the edge of acell, it transmits at a higher power level, relative to other unitswithin its cell and the adjacent cell, to reach the intended basestation. But, its signal is also received by the unintended basestation, i.e., the base station in the adjacent cell. Depending on therelative power level of two same-carrier frequency signals received atthe unintended base station, it may not be able to properly identify asignal transmitted from within its cell from the signal transmitted fromthe adjacent cell. What is needed is a way to reduce the subscriber unitantenna's apparent field of view, which can have a marked effect on theoperation of the forward link (base to subscriber) by reducing theapparent number of interfering transmissions received at a base station.A similar improvement is needed for the reverse link, so that thetransmitted signal power needed to achieve a particular receive signalquality can be reduced.

BRIEF DESCRIPTION OF THE PRESENT INVENTION

The present invention provides an inexpensive antenna apparatus for usewith a mobile subscriber unit in a wireless same-frequencycommunications system, such as a CDMA cellular communications system.

The invention provides an apparatus and method for efficientlyconfiguring the antenna apparatus to maximize the effective radiatedand/or received energy. The antenna apparatus includes multiple antennaelements and a like number of adjustable weight control components. Asis well known in the art, the weight control components are controllableto adjust the phase, amplitude, phase and amplitude and/or delay of thesignal coupled to each of the antenna elements. The weight controlcomponents (e.g., phase shifter, delay line, amplifier with variablegain) are jointly and independently operable to affect the direction ofreverse link signals transmitted from the subscriber unit on each of theantenna elements and the receiving direction for forward link signalstransmitted to the subscriber unit.

Further, the present invention provides an apparatus and method forinitiating antenna angle re-scans during which the antenna issequentially pointed in a plurality directions away from the primarydirection so that the antenna directivity can be dynamically adjusted tocompensate for changing radio frequency environments. It is advantageousto execute the re-scan process as pedestrian movement or other changesin the physical environment at the subscriber unit can modify thedirection from which the best signal is received by the subscriber unitas transmitted by the base station (or vice versa). The antenna istherefore controlled to change its steered direction to achieve theoptimum signal performance between the subscriber unit and the basestation,

It is further advantageous, according to the teachings of the presentinvention, to identify certain advantageous times for executing there-scan process to minimize interruptions to the data transmission andminimize the loss of data packets, thereby maintaining optimum systemperformance.

Prior to execution of the re-scan process, the antenna has been pointedin a current or primary direction, for receiving or transmitting data,as determined by the setting of the weight control components. Todetermine whether another direction might offer an improvement in signalquality, the antenna is rescanned to one or more different directions(also referred to as scan angles) and one or more signal quality metricsof interest are measured at each of those scan angles. The signalquality metric at each of these scan angles is compared with the signalquality metric at the primary or current direction or scan angle todetermine whether the current scan angle should be changed to anotherangle where an improvement in the signal quality metric can be attained.Thus, by controlling the weight control components, the antennaapparatus functions as a beam former for transmission of signals fromthe subscriber unit and as a directional antenna for signals received bythe subscriber unit such that a particular signal quality metric ofinterest is optimized.

Through the use of an array of antenna elements and execution of there-scan process, the antenna apparatus increases the effective transmitpower per bit transmitted. Thus, the number of active subscriber unitsin a cell may remain the same while the antenna apparatus of thisinvention allows for an increase in data rates for each subscriber unitbeyond those achievable by prior art antennas. Alternatively, if datarates are maintained at a given rate, more subscriber units may becomeactive in a cell using the antenna apparatus described herein. In eithercase, the cell capacity increases, as measured by the sum total of databeing communicated at any time.

In accordance with the teachings of the present invention, forward linkcommunications capacity can be increased as well, due to the directionalreception capabilities of the antenna as optimized during the re-scanprocess. Since a properly directed antenna is less susceptible tointerference from adjacent cells, the forward link cell capacity can beincreased by adding more users or by increasing cell radius.

With respect to the physical implementation of the antenna, oneembodiment of the present invention specifies that first, second, andthird antenna elements are positioned at locations corresponding tocorners of an equilateral triangle and are aligned orthogonal to a planedefined by the triangle. Other embodiments specify that first, second,third and fourth antenna elements are positioned at locationscorresponding to corners of a rectangle or square, with the fifthantenna element positioned at a location corresponding to approximatelythe center of thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the figures. The drawings are not necessarilyto scale, emphasis instead being placed upon illustrating the principlesof the invention.

FIG. 1 illustrates a cell of a CDMA cellular communications system.

FIG. 2 illustrates a preferred configuration of an antenna apparatusused by a mobile subscriber unit in a cellular system according to thisinvention.

FIGS. 3, 4, 5 and 6 are flow charts of the processing steps performedduring the antenna rescan process of the present invention.

FIG. 7 is a schematic diagram of an apparatus for identifying theoptimum signal quality metric.

FIG. 8 illustrates another antenna embodiment to which the teachings ofthe present invention can be applied.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates one cell 50 of a typical CDMA cellular communicationsystem. The cell 50 represents a geographical area in which mobilesubscriber units 60-1 through 60-3 communicate with a centrally locatedbase station 160. Each subscriber unit 60 is equipped with an antenna100 configured according to the present invention. The subscriber units60 are provided with wireless data and/or voice services by the systemoperator and can connect devices such as, for example, a laptopcomputer, a portable computer, a personal digital assistant (PDA) or thelike through base station 160 to a network 75, which can be the publicswitched telephone network (PSTN), a packet switched computer network,such as the Internet, a public data network or a private network orintranet. The base station 160 communicates with the network 75 over anynumber of different available communications protocols such as primaryrate ISDN, or other LAPD based protocols such as IS-634 or V5.2, or evenTCP/IP if network 75 is a packet based Ethernet network such as theInternet. The subscriber units 60 may be mobile in nature and may travelfrom one location to another while communicating with the base station160. As a subscriber unit leaves one cell and enters another, thecommunications link is handed off from the base station of the exitingcell to the base station of the entering cell. In another applicationthe subscriber units may maintain a relatively-fixed position withrespect to the base station 160. For example, a subscriber unit may be alaptop computer operated in the user's home. The user may move thelaptop computer from one location to another within the house. Each suchmove does not significantly change the distance between the base stationand the subscriber unit, but each move can significantly alter the radiofrequency characteristics of the communications link between the basestation and the subscriber unit.

FIG. 1 illustrates one base station 160 and three mobile subscriberunits 60 in a cell 50 by way of example only and for ease of descriptionof the invention. The invention is applicable to systems includingtypically many more subscriber units communicating with one or more basestations in an individual cell, such as the cell 50.

It is also to be understood by those skilled in the art that FIG. 1 maybe a standard cellular type communications system employing differingsignaling schemes such as a CDMA, TDMA, GSM or others in which the radiochannels are assigned to carry data and/or voice between the basestation 104 and subscriber units 60. In a preferred embodiment, FIG. 1is a CDMA-like system, using code division multiplexing principles suchas those defined in the IS-95B standards for the air interface.

The invention provides the mobile subscriber units 60 with an antenna100 that provides directional reception of forward link radio signalstransmitted from the base station 160, as well as directionaltransmission of reverse link signals, via a process called beam forming,from the mobile subscriber units 60 to the base station 160. Thisconcept is illustrated in FIG. 1 by the example beam patterns 71 through73 that extend outwardly from each mobile subscriber unit 60 more orless in a direction for best propagation toward the base station 160. Bybeing able to direct transmission more or less toward the base station160, and by being able to directively receive signals originating moreor less from the location of the base station 160, the antenna apparatus100 reduces the effects of intercell interference and multipath fadingfor the mobile subscriber units 60. Moreover, since the transmissionbeam patterns 71, 72 and 73 are extended outward in the direction of thebase station 160 but are attenuated in most other directions, less poweris required for transmission of effective communications signals fromthe mobile subscriber units 60-1, 60-2 and 60-3 to the base station 160.

FIG. 2 illustrates a detailed isometric view of a mobile subscriber unit60 and an associated antenna apparatus 100 configured according to oneembodiment of the present invention. Antenna apparatus 100 includes aplatform or housing 110 upon which are mounted five antenna elements 101through 105. Within housing 110, the antenna apparatus 100 includesweight control elements 111 through 115, a bi-directional summationnetwork or splitter/combiner 120, a transceiver 130, and a controller140, which are all interconnected via a bus 135. As illustrated, theantenna apparatus 100 is coupled via the transceiver 130 to a laptopcomputer 150 (not drawn to scale). The antenna 100 allows the laptopcomputer 150 to perform wireless data communications via forward linksignals 180 transmitted from the base station 160 and reverse linksignals 170 transmitted to the base station 160.

In this embodiment, each antenna element 101 through 105 is disposed onthe surface of the housing 110 as illustrated in FIG. 2. Here, fourelements 101, 102, 104 and 105 are respectively positioned at locationscorresponding to the corners of a rectangle, and a fifth antenna element103 is positioned at a location corresponding to the approximate centerof the rectangle. The distance between each element 101 through 105 isgreat enough so that the relationship between a signal received by morethan one element 101 through 105 will be out of phase with otherelements that also receive the same signal, assuming all elements 101through 105 have the same phase setting for their respective weightcontrol components 111 through 115.

However, according to the operation of the antenna 100 in thisinvention, the weight control components 111 through 115 are adjustableto affect the directionality of signals to be transmitted and/orreceived to or from the subscriber unit (i.e., laptop computer 150 inthis example). By properly adjusting the weight control components foreach element 101 through 105, the reverse link signal 170 (includingcontributions from each of the antenna elements 101 through 105) isformed that is positionally directed in the direction offering theoptimum reception of the signal transmitted by the base station 160.That is, the optimal arrangement for the weight control components forsending a reverse link signal 170 from the antenna 100 is a phasesetting for each antenna element 101 through 105 that creates adirectional reverse link signal beam former. The result is an antenna100 that directs a stronger reverse link signal pattern in the directionproviding the optimum received signal at the base station 160.

The positions of the weight control components used for transmission ofthe reverse link signal 170 also cause the elements 101 to 105 tooptimally receive forward link signals 180 transmitted from the basestation 160. Due to the controllable nature and the independence of theweight control components for each antenna element 101 through 105, onlythose forward link signals 180 transmitted from the base station 160that are intended to be received at the subscriber unit 60 are optimallyreceived. The elements 101 through 105 reject other signals that are notintended for the particular subscriber unit 60. In other words, adirectional antenna is formed by adjusting the weight control componentsof each element 101 through 105.

The summation network 120 is coupled to the signal terminal S, of eachweight control component 111 through 115. During signal transmission,the summation network 120 provides a reverse link signal to each of theweight control components 111 through 115. The weight control components111 through 115 impart a weight (i.e., affecting the amplitude, phase oramplitude and phase) to the input signal, as determined by a controlinput signal P provided to each weight control component 111 through 115by the controller 140. Applying a weight value to the reverse linksignals 170 transmitted from each element 101 through 105, causesconstructive or destructive interference with the signals transmittedfrom the other elements. In this manner, constructively interferingsignals combine to form a strong composite beam for the reverse linksignals 170 in the desired direction. The weight provided to the signaltransmitted from each antenna element 101 through 105 determines thedirection in which the stronger composite beam is transmitted.

The weight control components used for transmission from each antennaelement 101 through 105, also provide a similar physical effect on aforward link frequency signal 180 that is received from the base station160. That is, as each element 101 through 105 receives a signal 180 fromthe base station 160, the respective received signals are initially outof phase with each other due to the location of each element 101 through105 upon base 110. However, each received signal is weighted by theweight control components 111 through 115 under control of the signal atthe P terminal thereof, as supplied by the controller 140. Theadjustment brings each signal in phase with the other received signals180. Accordingly, the signal quality metric associated with thecomposite received signal, produced by the summation network 120, isoptimized.

To optimally establish the weight value for each of the weight controlcomponents 111 through 115 of the antenna 100, weight control values areprovided by the controller 140. In one embodiment, the controller 140determines these optimum weights during idle periods when the laptopcomputer 150 is neither transmitting nor receiving payload orinformational data via the antenna 100. During this idle time, areceived signal, for example, a forward link pilot signal 190 that iscontinuously sent from the base station 160 and is received by eachantenna element 101 through 105 affects adjustment of the weight controlcomponents 111 through 115 to optimize reception of the pilot signal 190from the base station 160, such as by maximizing the received signalenergy or another selected signal quality metric.

The controller 140 thus determines and sets an optimal weight value foreach weight control component 111 through 115, based on an optimizedreception of the forward link pilot signal 190. When the antenna 100returns to the active mode for transmission or reception of informationsignals between the base station 160 and the laptop 150, the weightssupplied for each weight control component 111 through 115 remain as setduring the previous idle period.

Before a detailed description of the phase shift computation asperformed by the controller 140 is given, it should be understood thatthe invention is based in part on the observation that the location ofthe base station 160 in relation to any one mobile subscriber unit(i.e., laptop 150) is approximately circumferential in nature. That is,if a circle is drawn around a mobile subscriber unit 60 and base stationlocations are assumed to have a minimum of one degree of granularity,the base station 160 can be located at 360 possible angular locationswith respect to the subscriber unit 60. The combination of the fivephase shift values (one value for each of the weight control components111 through 115) associated with each antenna element 101 through 105,optimizes the antenna pattern through 360° of rotation. Depending uponthe phase shift values attainable from the weight control components 111through 115, a granularity of less than one degree can also be realized.Those skilled in the relevant art recognize that the antenna 100 cancomprise n elements for implementing the teachings of the presentinvention.

In addition to the establishing the optimal weights during idle periodsas discussed above, the present invention describes a rescan processduring which the antenna 100 is scanned to a plurality of directionalangles to determine the angle providing an optimum signal qualitymetric. FIG. 3 illustrates a software flowchart for determining therescan timing and executing the re-scan process in accordance with oneembodiment of the present invention. The illustrated process (as well asthe software processes shown in FIGS. 4, 5 and 6) can be executed by thecontroller 140 or a dedicated or general-purpose processor in thesubscriber unit 60.

The FIG. 3 process begins at a start step 200 and proceeds to a decisionstep 202 where the subscriber unit mode is determined. If the subscriberunit 60 is in the active mode (i.e. transmitting or receivinginformational data packets, also referred to as payload data) then theFIG. 3 process moves to a step 204 where a specifically identifiedsignal quality metric is checked to determine whether the metric isbelow a threshold value. The specific process for detecting andmeasuring the signal quality metrics are discussed in thecross-referenced applications identified above. Exemplary signal qualitymetrics that can be used in accordance with the present inventioninclude: the ratio of energy per bit (E_(b)) to interference (I_(o)),the ratio of energy per bit to thermal noise (N_(o)) the ratio of energyper bit to thermal noise plus interference (N_(o)+I_(o)), the energy perchip (E_(c)) to either the thermal noise, the interference, or the sumof the thermal noise and the interference, and the correlated power andthe signal to noise ratio (where the noise is defined as either thethermal noise, the interference or the sum of noise and interference).If the selected signal quality metric, as evaluated at the decision step204, is not less than the threshold value, this indicates that thecommunications link between the subscriber unit 60 and the base station160 is apparently functioning acceptably at the current directionalangle. Processing thus returns from the decision step 204 back to thedecision step 202. The frequency at which the signal quality metric ischecked at the decision step 204 can be timer-controlled by interposinga timer (not shown in FIG. 3) between the decision steps 202 and 204.

If the selected signal quality metric is below the threshold value,processing moves from the decision step 204 to a step 206 where the idlemode is initiated, i.e., the transmission and reception of theinformation signals is suspended. As discussed above, in the idle statethe subscriber unit is responsive to a pilot signal transmitted from thebase station 160. The signal quality metric is evaluated at various scanangles during execution of the re-scan process, as indicated at a step208. During the re-scan process, the weight control components 111through 115 are adjusted to move the antenna directional angle through aplurality of directional angles. Thus to execute the scan process, oneor more of the weight control component settings is changed, resultingin a change of the antenna directional angle. One technique for scanningthe antenna beam through various directional angles is described in theco-pending and co-owned issued patent entitled, “Method and Apparatusfor Adapting Antenna Array to Reduce Adaptation Time While IncreasingArray Performance”, U.S. Pat. No. 6,473,036 issued on Oct. 29, 2002,wherein a two-step process is utilized for adjusting the weight controlcomponents 111 through 115. Irrespective of the specific processutilized for changing the antenna directional angle. Once a newdirectional angle is established, a specified signal quality metric isdetermined for the pilot signal at that angle. After the signal qualitymetric has been measured at a predetermined number of directional anglesor after the rescan process has continued for a predetermined time, thesignal quality metric values are analyzed to identify the optimum value.At a step 210, the weight control components 111 through 115 are thenadjusted to the directional angle associated with the optimum signalquality metric. From the step 210, processing moves to a step 212 forreactivating the active mode, followed by return to the decision step202. As will be discussed herein below, rescanning can also be performedduring the active operational mode on known data.

Returning to the decision step 202, if the subscriber unit 60 is not inthe active mode, (i.e., the operative mode is the idle mode) processingmoves to a step 220 where a timer is set, followed by a decision step222 where the timer status is determined. If the timer has not expired,processing continues looping through the decision step 222 as shown.When the timer expires, a re-scan is executed at a step 224. The rescanprocess executed at this stage of the process is identical to thatdescribed in conjunction with the step 208. Following completion of there-scan, the subscriber unit 60 returns to the idle mode at a step 226.Later, when the subscriber unit wishes to transmit an information signalto the base station 160, a channel assignment is requested at a step228. At this point, it is preferable to have already identified the bestdirectional angle so that the weight control components 111 through 115can be set to achieve that angle either immediately before orimmediately after the channel assignment is requested. With the optimumdirectional angle established and implemented prior to the request for achannel assignment, system latency is reduced. However, in anotherembodiment of the present invention, another rescan can be executed (seea step 230) after a channel assignment is requested. For instance, ifthe time between the re-scan at the step 224 and the channel assignmentrequest is less than a predetermined time, then it is acceptable to usethe directional angle identified during the step 224 re-scan process.If, however, the elapsed time is greater than this predetermined value,it is advantageous to execute another re-scan as illustrated by the step230. In any case, the channel assignment is received as indicated at astep 232 and the active mode is initiated as shown at a step 234. Oncethe active mode is initiated, the antenna directional angle, asdetermined by the setting of the weight control components 111 through115 to implement the optimum identified signal quality metric, ismaintained so long as the channel assignment received at the step 323 ismaintained. Of course, if the signal quality metric of choice fallsbelow a predetermined threshold, while the subscriber unit 60 is in theactive mode, then the process beginning at the decision step 204 isexecuted to locate a new directional angle for the antenna 100. Inaddition to initiating the rescan process in response to a channelassignment request, in other embodiments of the present invention, otherevents can be used to trigger the rescan, such as movement between cellsectors or other link layer events (where the link layer is as definedin the OSI network model).

Another embodiment of the present invention is depicted in the flowchartof FIG. 4 where an idle mode rescan is executed on a predeterminedfrequency cycle. The process begins at a start step 250 and proceeds toa decision step 252. If the subscriber unit 60 is in the active mode,processing loops back to the input of the decision step 252, asindicated by a continue step 254. When in the active mode, in lieu ofthe continue step 254, the re-scan processes as set forth in FIG. 3(beginning at the step 204) or as set forth in FIG. 5 (to be discussedfurther herein below) can be implemented.

If the subscriber unit 60 is not in the active mode, processing proceedsfrom the decision step 252 to a step 256 where the re-scan process isbegun and continues. If the re-scan process is interrupted by a channelassignment request (see a decision step 258) then the subscriber unit 60switches to the active mode, as indicated at a step 260. As thesubscriber unit 60 initiates the active mode, there are severalavailable choices for the antenna directional angle. According to oneembodiment of the present invention, the directional angle employed canbe the angle used during the last transmission from the subscriber unit60 to the base station 160. Alternatively, the optimum directional anglecan be determined by evaluating the signal quality metric valuesmeasured at the step 256 before the rescan process was interrupted bythe channel assignment request. In yet another embodiment, when therescan process is interrupted by the channel assignment request, thechannel assignment can be delayed until after the rescan processexecuted at the step 256 is complete. In this later embodiment,effectively the steps 262, 264, 266 and 268 are executed before thechannel is assigned by the base station 160.

Returning to the FIG. 4 embodiment, until a channel assignment isrequested (see the negative result from the decision step 258) there-scan process continues as illustrated at the step 262. The decisionstep 264, determines when all potential angles have been scanned. In oneembodiment, this can involve the scanning of 360° at a predeterminedangle per scan, such as the one degree of granularity discussed above.In another embodiment, a scan sector can be determined based on theapproximate relative position of the subscriber unit 60 and the basestation 160. In this embodiment only angles within that sector arescanned. Angles outside the sector are not checked because they may havea low probability of producing a signal quality metric better thandirectional angles within the sector. However, the chosen sector may notproduce the optimum signal quality metric as interferencecharacteristics can influence the signal quality metric for directionalangles both within and without the sector, thus producing an optimumsignal quality metric at a directional angle outside the sector. Afterthe antenna has been scanned through each of the candidate scan anglesand the signal quality metric from each determined, processing moves toa step 266 where the signal quality metric for each angle scanned isevaluated and the optimum value selected. At a step 268, the weightcontrol components 111 through 115 are adjusted to the scan angleselected at the step 266. In various embodiments of the presentinvention, the scan or directional angle selected at the step 268 can beemployed for a predetermined period of time, until the next channelassignment request, until the occurrence of another link layer event, oruntil a signal quality metric falls below a predetermined threshold.Following the step 268 the process returns to the decision step 258,where the affirmative branch is selected when a channel assignment isrequested.

FIG. 5 illustrates another rescan methodology that involves puncturingthe active mode data transmissions to or from the subscriber unit 60 toexecute a rescan. Data bits transmitted during this puncture period arelost at the receiver because the receiver circuitry is occupied with therescan process. The FIG. 5 process begins at a start step 300 andcontinues to a decision step 302. If the subscriber unit is not in theactive mode then the FIG. 5 process loops back through the decision step302. In lieu of simply looping back to the decision step 302, thenegative path therefrom can include any of the various idle mode rescanprocesses discussed herein, including the FIG. 3 process beginning atthe step 220. The FIG. 5 process takes advantage of the forward errorcorrecting process employed at the receiver (the subscriber unit 60 forreverse link signal and the base station 160 for forward link signals)to detect and correct errors in the received bit stream. Such forwarderror correcting techniques, which are well known in the art, requirethe inclusion of forward error correcting bits to the each data word inthe bit stream. The number of these bits, referred to as a checksum,appended to a data word determines the forward error correcting power,i.e., the number of errors that can be detected and corrected in thedata word. Thus, to ensure that the receiver can recover the correctdata word from a punctured data word, the puncture period must belimited in duration to the number of lost bits that the checksum candetect and correct. Higher data rates require shorter puncture periods.

In another embodiment, if the period during which the data is to bepunctured is coordinated between the base station 160 and the subscriberunit 60, and therefore known a priori, the sending unit can increase thechecksum length during the puncture period to increase the number ofdetectable and correctable errors in the received data word. This isadvantageous as the receiving unit's ability to detect and correcterrors due to thermal noise during the puncture period is degraded,because the checksum bits are required to detect and correct the errorscaused by puncturing through the data bits.

Returning to the FIG. 5 process, if the subscriber unit 60 is in theactive mode, processing continues on the affirmative branch of thedecision step 302. A first timer is set at a step 304 and processingloops around a decision step 306 until the first timer expires. At thatpoint, the data receiving or transmitting process is interrupted (i.e.,the data puncturing begins) and a rescan of candidate directional anglesbegins. See a step 308. Although the rescan process is initiated basedon a timer value, it is known by those skilled in the art that otherevents can be used as the trigger for the rescan. The system operatormust achieve a compromise rescan frequency. Rescanning too frequently tooptimize the signal quality metric may degrade system performance byincreasing latency. During the rescan process, the subscriber candetermine the signal quality metric using the pilot signal 190 (whichmeans effectively, that the subscriber unit has entered the idle mode)or using known data transmitted from the base station 160.

A second timer for controlling the rescan period, which is a function ofthe forward error correcting power as discussed above, is set at a step309. At a decision step 310 the second timer value is checked and whenthe second timer expires, processing moves to a decision step 311 fordetermining whether all the potential directional angles have beenevaluated. If the re-scan process was terminated without evaluation ofall potential angles, the result at the decision step 311 is negativeand processing continues to a step 312, where the transmission orreception of data packets is restarted. From the step 312, the timer isreset at the step 304 and the re-scan process begins anew when the firsttimer expires.

If the decision step 311 result is affirmative, at a step 314 theoptimum directional angle is identified based on the signal qualitymetric at each of the candidate directional angles. Following theselection of a new primary directional angle, the process moves to astep 316 where the flow of data packets is reinitiated. In anotherembodiment, the step 316 is followed by a step for checking the signalquality metric of the received signal and if it drops below apredetermined threshold, a rescan is initiated. See for example, thestep 904 of FIG. 3.

As is known by those skilled in the art, the subscriber unit 60 includesa number of control loops for demodulating and detecting the receivedsignal and operative also in the transmit mode. Exemplary control loopsinclude automatic frequency control loops, automatic gain control loops,digital locked loops and phase locked loops. It is also known that tomaintain these loops in a locked condition it is necessary that theyprocess incoming signals. Thus, if the rescan process continues for atime beyond which these loops can maintain a locked condition, one ormore of the loops may become unlocked. Thus, in one embodiment, it isnecessary to terminate the rescan process (by way of the second timer309 in FIG. 5) and return to the processing of informational data tomaintain the loops in the locked condition. Thus, in various embodimentsit is necessary to determine the second timer value based on the forwarderror correcting power and/or the time during which one or more of thecontrol loops can maintain a locked condition.

FIG. 6 illustrates generally the process steps executed during a rescanof candidate directional angles for the antenna 100. A rescan isinitiated as shown by a step 350 under several conditions as discussedabove. For example, when a selected signal quality metric drops below apredetermined threshold value a re-scan is initiated. In the idle oractive mode, a timer can be set upon the occurrence of a specified eventand a re-scan initiated when the timer has expired. In anotherembodiment, a re-scan is initiated either prior to or immediatelyfollowing a channel assignment request issued by the subscriber unit160.

Once the re-scan has been initiated, the process proceeds to a step 352where certain control loop parameters must be maintained. For instance,the subscriber unit 60 includes an automatic gain control loop, anautomatic frequency control loop and a digital locked loop, each loopoperating with certain parameters that maintain the loop in a lockedconfiguration. These locked loop parameters must be maintained duringthe re-scan process so that when the subscriber unit 60 returns to theprimary antenna direction, the loops will immediately engage in a lockedstate. The loop parameters can be stored during the rescan process andthe stored values used when the antenna 100 returns to the primarydirection for transmitting and receiving information data packets.Otherwise, each loop must regain its locked state, which takes a finiteamount of time, when the antenna 100 returns to the primary direction.In lieu of maintaining the control loop parameters by storing them, thesubscriber unit 60 can return to the primary direction at a specifiedfrequency, thereby allowing the control loops to remain in a lockedstate. The frequency at which the subscriber unit 60 returns to theprimary direction depends on the time constant of each control loop. Ifthe time constant of one control loop is shorter than the re-scan time(defined as the time during which the subscriber unit 60 moves to a newscan angle, checks the signal quality metric there and returns to theprimary direction) then the control loop parameters must be stored sincethe locked condition cannot be maintained while the antenna is scanningaway from the primary direction.

At a step 354, the antenna scans to a new direction by changing theweight control components 111 through 115. A selected signal qualitymetric is measured at step 355. Potential signal quality metrics includethe received power, the received signal to noise ratio, the correlatedpower, the ratio of the energy per bit (E_(b)) to either the totalthermal noise (N_(o)), the total interference (I_(o)) or the sum of thethermal noise and the total interference. In lieu of the energy per bit,the energy per chip (E_(c)) can be used as a signal quality metric.

In one embodiment, both the base station 160 and the subscriber unit 60perform the signal quality metric evaluation. The subscriber unit 60utilizes the pilot tone transmitted from the base station 160 for thismeasurement. The base station 160 utilizes a known set of datatransmitted by the subscriber unit 60. The directional angle of thetransmission received at the base station 160 must be known so that themeasured signal quality metric can be associated with the correctdirectional angle. To accomplish this, the base station determines therescan start time and must know the scan pattern. These two factorsallow the base station 160 to correlate each signal quality metricmeasurement with the correct scan angle. Alternatively, the known signaltransmitted from the subscriber unit 60 for measuring the signal qualitymetric at the base station 160 includes a portion representative of thedirectional angle. The directional angle information can thus be easilyassociated with the directional angle at the base station 160. Thus, thesignal received at the subscriber unit 60 provides for an evaluation ofthe reverse link scan angles, and the signal evaluation at the basestation 160 provides an evaluation of the forward link quality.

The FIG. 6 process then moves to a decision step 358 to determinewhether the scanning process is complete. The scanning process can betime limited; therefore when the time has expired the scanning processis concluded and the antenna 100 returns to the primary directionalangle. Alternatively, the scanning process can cover a predeterminednumber of directional angles and when that number has been evaluated,the scanning process terminates. Further, to limit the scanning period,the scanning process can continue until a signal quality metric exceedsa predetermined value. Although this will likely not produce the optimumsignal quality metric, it is a technique that effectively reduces thescanning time, representing a compromise between finding the optimumsignal quality metric and arriving at an acceptable signal qualitymetric before all the angles have been scanned. In yet anotherembodiment, the scanning process can be executed during a series ofsuccessive scan intervals wherein different angles are scanned andevaluated during each interval, wherein the angles may not becontiguous. Finally, it is also possible to conduct a partial signalquality metric evaluation at a given scan angle during one re-scan andreturn to that angle during a subsequent scan period to complete theevaluation. As can be appreciated by those skilled in the art, there areseveral scan methodologies available.

In the embodiment, when the rescanning occurs during the active modeusing informational data bits (rather than the pilot signal or knowndata bits), the data bits received at a directional angle can be used tomaintain the primary direction control loops, so long as the signalquality metric at that directional angle exceeds a predeterminedthreshold. If the signal quality metric is below the threshold value,the received data packets cannot be used to maintain the control loopsand in some cases it may not be possible to demodulate and detect thedata packets. In the latter case, the forward error correction processdetects and corrects the lost data symbols. Note that this processwherein the primary directional antenna angle and the control loops areupdated during the rescan process using the received data symbols can beused only when the data symbols at the new directional angle aretime-aligned with the data symbols at the previous directional angle.

When the rescan process is complete, the decision step 358 produces anaffirmative response followed by a step 360, where the signal qualitymetric information is transferred between the base station 160 and thesubscriber unit 60. As discussed above, the base station 160 hasacquired signal quality metric information for the forward link and thesubscriber unit 60 has acquired signal quality metric information forthe reverse link. In one embodiment, the subscriber unit 60 analyzes thesignal quality metric information for both the forward link and thereverse link. In this embodiment, the forward link signal quality metricinformation collected at the base station 160 must be transferred fromthe base station 160 to the subscriber unit 60 so that the forward linkevaluation can be performed at the latter. Alternatively, if the basestation 160 analyzes the forward and reverse link signal qualityinformation and selects the optimum directional angles for each link,then the subscriber unit signal quality metric information istransmitted thereto at the step 360. Generally, whenever the signalquality metric evaluation is performed at other than the site where thedirectional angle is set, then the signal quality metric informationmust be transferred to the other site for use in establishing thedirectional angle. Note that as an alternative embodiment to the processillustrated in FIG. 6, the step 360 can be relocated immediately priorto the decision step 358. In this embodiment signal quality metricinformation is transferred between the base station 160 and thesubscriber unit 60 immediately following evaluation of the signalquality metric at the scanned angle. As indicated at a step 362 anantenna angle or direction is selected for the forward link and thereverse link. Likely these two angles will not be identical.

Typically, a system constructed according to the teachings of thepresent invention operates in a full duplex mode. However, in anembodiment where the antenna 100 does not change directional angles whenswitching from the forward to the reverse link (or vice versa) an anglemust be selected for use on both the forward and reverse links at thesubscriber unit 60, and the selected angle should represent acombination of the optimum selected forward and reverse link directionalangles. For instance, if the majority of the data is being carried onthe forward link, then a subscriber unit directional angle that favorsthe optimum forward link directional angle should be used.Alternatively, the combination angle may be selected to ensure that oneor both links maintain a minimum signal quality metric.

In yet another embodiment (not illustrated in FIG. 6) the signal qualitymetric data accumulated for each scanned directional angle is stored forlater analysis to identify the optimum directional angle. As discussedabove, this analysis can be performed at the base station 160 or thesubscriber unit 60 so long as the relevant data is present at theevaluation site. Alternatively, during the rescanning process thesubscriber unit 60 can sequentially compare each signal quality metricvalue with the immediately preceding signal quality metric value andselect the best directional angle on the basis of that comparison. Inthis mode, once the re-scan period has ended, the subscriber unit 60utilizes the identified optimum scan angle for data transmission andreception.

In yet another embodiment of the present invention (not illustrated inFIG. 6) the re-scanning process is performed in a deterministic patternknown a priori by both the subscriber unit 60 and the base station 160.In the conventional CDMA cellular system, the base station 160 commandsthe subscriber unit 60 to a higher (or lower) power level when thesignal received at the base station 160 falls below (or above) apredetermined threshold. In the embodiment discussed above where thesignal quality metrics of both the forward link and the reverse link areevaluated, it is necessary for the base station 160 to know when thesubscriber unit 60 is transmitting informational data and when it istransmitting known data merely for the determination of a signal qualitymetric. If the base station 160 cannot or does not distinguish betweeninformational data and known data, it may command the subscriber unit 60to increase the output power level during transmissions that areintended for determining the signal quality metric. Thus, it isadvantageous to perform coordinated reverse and forward link checks sothat the base station 160 does not unnecessarily command the subscriberunit 60 to change its output power. A clock signal synchronized at thebase station 160 and the subscriber unit 60, in conjunction with apredetermined a priori rescan time, can be used at the base station 160to determine when the subscriber unit 60 is in a re-scan mode. In lieuof using a clock signal, the base station 160 can search for a knowndata pattern in the received signal and thereby determine that thesubscriber unit 60 is engaged in the re-scan process. The base station160 does not exercise power control over the subscriber unit 60 when thelatter is re-scanning in search of a better directional angle.

FIG. 7 illustrates a schematic of electronic components for implementinga perturbational algorithm to determine optimal weight settings for eachantenna element 101 through 105.

The algorithm fixes a value for four of the five unknown, optimum weightsettings W[i], e.g. W[2] through W[5]. The algorithm perturbs the systemand observes the response, adapting to find the optimum arrangement forthe unfixed weight, e.g.,. W[1]. The measured link quality metric, inthis embodiment E_(c)/I_(o), is fed to a second gain block G2. Aconstant G is input to a first gain block G1. A first fast clock, CLK1,which alternates from a value of “1” to a value of “−1” is inverted byI1 and fed to a first multiplier M1. The other input of multiplier M1 isfed by the gain block G1.

The output of M1 is fed to a second multiplier M2 together with theoutput of the second gain block G2. An integrator N1 measures an averagelevel and provides this value to the latch L. A slow clock CLK2,typically alternating at a rate which varies between “1” and “0” and ismuch slower than CLK1 (by at least 100 times) drives the latch clock C.The output of the latch L is summed by summation block S with thenon-inverted output of M2. The result, W[i], is a value which tends toseek a localized minimal value of the function to be optimized.

The process shown in FIG. 7 is then repeated by setting the first weightcontrol components to W[1] and then determining W[2] by varying W[3] toW[5] in accordance with the FIG. 7 process. The process continues tofind the optimum value for each of the five unknown weights.

Alternatively, instead of incrementally varying the weights for eachantenna element 101 through 105, the weight for each element can bestored in a table of vectors, each vector having five elementsrepresenting the five weight settings for the weight control components101 through 105. The five values in each vector can be computed inadvance based upon the angle of arrival of the received pilot signal.That is, the values for each antenna element are predetermined accordingto the direction in which the base station is located in relation to themobile subscriber unit. In operation, to scan the antenna directionalangle, a vector is selected and the elements thereof are used as theweights applied by the weight control components 111 through 115.Further, in another embodiment if the angle of arrival of the optimumsignal can be determined, then that angle is used as an index into thevector table, to set the optimum directional angle. In this embodiment,only the single angle of arrival calculation needs to be performed toproperly set the weights for each antenna element 101 through 105.

The antenna apparatus in preferred embodiments of the invention isinexpensive to construct and greatly increases the capacity in a CDMAinterference limited system. That is, the number of active subscriberunits 60 within a single cell in a CDMA system is limited in part by thenumber of frequencies available for use and by signal interferencelimitations that occur as the number of frequencies in use increases. Asmore frequencies become active within a single cell, interferenceimposes maximum limitations on the number of users who can effectivelycommunicate with the base station. Intercell interference (i.e., by andbetween adjacent cells) from other subscribers is also a limiting factorto cell capacity. The present invention provides an increase in cellcapacity by the identification of an optimum directional angle for eachsubscriber unit 60

Since this invention adaptively eliminates interference from adjacentcells and selectively directs transmission and reception of signals fromeach subscriber unit 60 equipped with the invention to and from the basestation 160, an increase in the number of users per cell is realized.Moreover, the invention reduces the required transmit power for eachsubscriber unit 60 by optimizing the directional angle between thesubscriber unit 60 and the base station 160.

Alternative physical embodiments of the antenna include a four elementantenna wherein three of the elements are positioned at corners of anequilateral triangular plane and are arranged orthogonally and extendoutward from that plane. The fourth element is similarly situated but islocated in the center of the triangle. Further, the teachings of thepresent inventions are applicable to an antenna comprising a pluralityof elements, where less than all of the elements are active elements,i.e., for radiating or receiving a signal where the other elements serveas parasitic elements to reflect, redirect or absorb some portions ofthe emitted signal to advantageously shape the transmitted beam in thetransmit mode and similarly advantageously affect the receive beampattern. The elements can be operative in either the active or parasiticmode as determined by an element controller.

FIG. 8 illustrates such an antenna embodiment including both parasiticand active elements. Parasitic elements 500 and 502 are connectedrespectively to terminations 504 and 506. An active element 508 isconnected to conventional receiving circuitry 5 10, such as that shownin FIG. 2. Although FIG. 8 illustrates two parasitic elements and asingle active element, it is known by those skilled in the art that thefundamentals associated with FIG. 8 are extendable to n parasiticelements and m active elements. In one embodiment, for instance, theteachings of the present invention can be applied to four parasiticelements arranged at the corners of a rectangle and the active elementat approximately the rectangle center.

In operation, a signal is received at each of the parasitic elements 500and 502 as shown. The signal is then carried to the terminations 504,506, respectively, and reflected back therefrom through the elements 500and 502. The terminations 504 and 506 comprise any one of the following:a phase shifting device, a weight control component (such as the weightcontrol components 111 through 115 of FIG. 2) an impedance terminationand a switch. The terminations 504 and 506 control both the amplitudeand phase, only the phase, or only the amplitude of the signal inputthereto, and thereby produce a reflected signal having a certainrelationship (i.e., amplitude and phase characteristics) with respect tothe received signal. The reflected signals are radiated from theelements 500 and 502, and effectively combined upon receipt at theactive element 508. It is seen that the FIG. 8 embodiment accomplishesthese three primary objectives of an antenna array: receiving the signalat an element, imparting a phase or amplitude shift to the receivedsignal and combining the received signals. Although the FIG. 8configuration has been explained in the receiving mode, it is known bythose skilled in the art that in accordance with the antenna reciprocitytheorem a like a function is achieved in the transmit mode.

While this invention has been particularly shown and described withreferences to preferred embodiments, those skilled in the art willrealize that various changes in form and details may be made thereinwithout departing from the spirit and scope of the invention as definedby the appended claims. Those skilled in the art will recognize or beable to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. For example, there can be alternative mechanisms for determiningthe proper phase for each antenna element, such as storing phase anglesin a linked list or a database instead of a table. Moreover, thoseskilled in the art of radio frequency measurement techniques understandthere are various ways to detect the angle of arrival and signal qualitymetrics of a signal, such as the received pilot signal or a known datasignal. These mechanisms for determining the signal angle of arrival andsignal quality metrics are meant to be contemplated for use by thisinvention. Once the location is then known, the proper phase settingsfor weight control components may be quickly obtained. Such equivalentsare intended to be encompassed within the scope of the claims.

1. A method for operating an antenna in a wireless communicationssystem, the antenna comprising a plurality of antenna elements forgenerating a plurality of antenna patterns, the method comprising:adjusting weights for the plurality of antenna elements to establish acurrent antenna pattern; detecting a signal received at each of theplurality of antenna elements in the current antenna pattern; combiningthe signal received at each of the plurality of antenna elements toproduce a combined received signal; determining a signal quality metricfor the combined received signal; adjusting the weights for theplurality of antenna elements to establish at least one candidateantenna pattern; repeating the detecting, the combining and thedetermining each one candidate antenna pattern; comparing the signalquality metric associated with the current antenna pattern to the signalquality metric associated with the at least one candidate antennapattern for determining a preferred signal quality metric; and adjustingthe weights for the plurality of antenna elements associated with thepreferred signal quality metric to establish a preferred antennapattern.
 2. A method according to claim 1 wherein adjusting the weightsfor the plurality of antenna elements changes at least one of anamplitude and a phase of the received signal associated therewith.
 3. Amethod according to claim 1 wherein the weights for the plurality ofantenna elements associated with the preferred antenna pattern are fixedfor a period during which information is transmitted over an assignedchannel.
 4. A method according to claim 1 wherein the weights for theplurality of antenna elements associated with the preferred antennapattern are fixed until a signal quality metric associated therewithdrops below a threshold.
 5. A method according to claim 1 wherein thepreferred signal quality metric corresponds to an increasedpower-to-interference ratio for the received signal associatedtherewith.
 6. A method according to claim 1 wherein the preferred signalquality metric corresponds to a reduced bit error rate for the receivedsignal associated therewith.
 7. A method according to claim 1 whereinthe preferred signal quality metric corresponds to an increasedcorrelated power for the received signal associated therewith.
 8. Amethod according to claim 1 wherein the antenna has a rectangularsurface; and wherein the plurality of antenna elements includes first,second, third and fourth elements positioned at locations correspondingto corners of the rectangle surface, and a fifth element positioned at alocation corresponding to an approximate center of the rectanglesurface.
 9. A method according to claim 8 wherein the antenna comprisesfirst, second, third, fourth and fifth weight control components foradjusting the respective weights associated with the first, second,third, fourth and fifth antenna elements.
 10. A method according toclaim 1 wherein adjusting the weights for the plurality of antennaelements is repeated for establishing a plurality of candidate antennapatterns; and wherein repeating the detecting, the combining and thedetermining are performed at each of the plurality of antenna elementsin each candidate antenna pattern.
 11. A method according to claim 10wherein the comparing is repeated for the signal quality metricassociated with each candidate antenna pattern.
 12. A method accordingto claim 10 wherein the adjusting, the repeating and the comparing arerepeated for the candidate antenna patterns until a signal qualitymetric exceeds a threshold.
 13. An antenna for use with a receiver in awireless communications system, the antenna comprising: a plurality ofantenna elements for generating a plurality of antenna patterns; a firstmodule for applying weights to a signal received at each of saidplurality of antenna elements to generate a selected one of the antennapatterns; a second module for detecting a received signal at each ofsaid plurality of antenna elements; a combiner for combining thereceived signal detected at each of said plurality of antenna elementsto produce a combined received signal for the selected antenna pattern;and a third module for determining a signal quality metric for thecombined received signal at each selected antenna pattern; said firstmodule being responsive to the determined signal quality metrics foradjusting the weights to generate a preferred antenna pattern.
 14. Anantenna according to claim 13 wherein said first module changes at leastone of an amplitude and a phase of the received signal associatedtherewith when applying the weights thereto.
 15. An antenna according toclaim 13 wherein said first module sets the weights for the plurality ofantenna elements associated with the preferred antenna pattern for aperiod during which information is transmitted over an assigned channel.16. An antenna according to claim 13 wherein said first module sets theweights for the plurality of antenna elements associated with thepreferred antenna pattern until a signal quality metric associatedtherewith drops below a threshold.
 17. An antenna according to claim 13wherein the preferred antenna pattern corresponds to a preferred signalquality metric.
 18. An antenna according to claim 17 wherein thepreferred signal quality metric corresponds to an increasedpower-to-interference ratio for the received signal associatedtherewith.
 19. An antenna according to claim 17 wherein the preferredsignal quality metric corresponds to a reduced bit error rate for thereceived signal associated therewith.
 20. An antenna according to claim17 wherein the preferred signal quality metric corresponds to acorrelated power that is increased for the received signal associatedtherewith.
 21. An antenna according to claim 13 wherein said pluralityof antenna elements comprise first, second, third, and fourth elementspositioned at locations corresponding to corners of a rectangle and afifth element positioned at a location corresponding to the approximatecenter of the rectangle.
 22. An antenna according to claim 21 furthercomprising first, second, third, fourth and fifth weight controlcomponents for adjusting the weights associated with said first, second,third, fourth and fifth antenna elements, respectively.
 23. An antennaaccording to claim 22 wherein said first, second, third, fourth andfifth weight control components are adjustable to provide apredetermined degree of rejection for signals received by the receiverbut not intended for the receiver.